Method of preparing pickled iron and steel for painting.



No'Drawing.

it I

JAMES H. GRAVELL, on NEW you, N. Y.

METHOD OF PREPABDTG lICKLED IRON STEEL FOB PAINTING.

To all cltom it may concern: 7

Be it known that I, JAMES H. Glmvnrig'a "citizen of the. United States, and a resident of. New York city, in the county of New York and State of New York, have invented a certain new and useful Method of Preparing Pickled Iron and Steel for Painting, of

which the following is a specification;

It is now well known that iron. and steel must be cleaned before they are painted in order that the applied paint may be permanent. Unless the: metal is properly prepared, rust forms under the paint and destroys the protective coating of paint, allowing the atmosphere to have free access to the metal thereby further'rusting it.

One of the methods used for preparing metals for painting isknown as pickling,

and consists in subjecting the metal to-the action of a sulfuric acid bath or a bath containing hydrochloric acid. These pickling baths remove thescale and rust and attack the surface of the metal, thereby ridding it of objectionable materials, and seemingly produce a clean surface on which ;to apply the paint, but it is well known that a pickled surface, after having been painted, will not remain free from rust.v This is due to small amounts of pickle remaining on the surface even though the metal has been washed.

That is, although washing removesa large percentage of thepickle, yet sufiicient remainsbehind to give trouble. In order to neutralize the small percentage of pickle remaining on the metal it is practical to treat the metal with lime-Water which, on drying,

I leaves the surface thinly coated with a pow mostly of a mixture of cal- Based on my discovery I have invented [a process by which picklediron and steel can be cheaply prepared for painting so ,thatthere is no danger of the metal rusting Specification of Letters Patent.

My metal by the regular pickling process with Patented Sept. 17, 1918.

. Application filed Apri-ISO, 19l8 Serial No. 231,688.

I under the paint and in fact no danger of the metal rusting while it is being fabrieated 0r-stored "prior to painting.

pickling acids :-sulfuric acid or hydrochloric acid and then giving the metal a second pickle in -a solution of phosphoric acid whlch removes the surface metalwhich has been inactual contact with the pickling method consists in first pickling the v agents in the first f operation. After these two pickling operations the metal is allowed to dry. If the painting operation is included in the treatment, the treatment can be considered a rust-proofing process as the surface of the metal remains free from rust even after the paint appears to have been entirely removed by the weather.

One of the ways of carrying out my process, commercially, consists 1n immerslng the metal in a bath of sulfuric acid heated nearly to a boiling;temperature -until the metal has been sufliciently cleaned; the metal is then removed from this bath and immersed in a bath of water to remove most of the sulfuric acid. The bath of water need not be heated but it should be constantly renewed; After removing the metal from the water bath, the metal is immersed in a bath of phosphoric acid or a salt of phosphoric acid which will produce the same result. The phosphoric acid bath may be coldand its strength can be altered to a great extent, depending on the future manipulations through which the metal is passed. I have found that one part by volume of 85% phosphoric acid and ten parts by volume of water produces satisfactory results.

After removing the work from the phosphoric acid bath it is allowed to-drain and Metal treated according to my method may be painted without danger of the metal rusting under the paint, and owing to the fact that no rust accumulates under the paint, the painted finish will be permanent. Although I have described my rocess in detail in connection with hot s ul uric acid pickle, it is evident that Imay substitute hydrochloric acid or may use a cold pickle 'without departing from my invention.

'In cases whereit is inconvenient to wash the metal prior to immersing it in the phosphoric acid solution, I have found that the- .addition of a small amount of calcium phosphate to the phosphoricacid bath neutralizes the acid which may be carried from the pickle.

I claim: 1. The method of preparing pickled iron and steel for ainting which consists in subjec'ting the pickled metal to the solvent action of phosphoric acid, substantially as described. Y

2. The method of preparing pickled iron 'and steel for painting which consists in washing the pickled metal, and then subjecting the washed metal to the solvent action of phosphoric acid, substantially as described.

3. The method of preparing iron and steel which consistsin pickling the iron or steel, subjecting the. pickled iron or steel to containing calcium the solvent action of phosphoric -acid, and

y then painting the iron'or steel, substantially as described. 4. The method metal with sulfuric acid to remove rust and scale, and then removing the surface metal which has contacted with the pickle by the of preparing metals for painting which consists in first pickling the action of a solution of phosphoric acid, sub- I stantiallyas described.'

5. The method of preparing iron and steel to oppose rusting consequent upon pickling which consists in first pickling the metal with sulfuric acid, and then removing the surface metal which has contacted with the pickle by a solutionof phosphoric acid hosphate. JAE

Es- H. GRAVELL. 

